Welcome to the deep of winter, the time when the nights are longest and you basically never want to get out of your warm bed. This is the perfect time to get sucked into a long, complicated relationship with a book series. But what book series are worth getting hooked on? We did some digging and soul searching, to find out.

Here are 10 book series that are so addictive, you'll wish they had an infinite number of titles. Note: We tried for a certain amount of variety in terms of genre, style and era with this selection. And we definitely couldn't include every addictive book series out there. So please list your own favorites below!

Top image: Shadow of the Torturer by Bruce Pennington.

1) Mike Carey's Felix Castor Novels

We've sung the praises of this series before — it's five books, very much in the same vein as the also-addictive Sandman Slim novels by Richard Kadrey and Dresden Files books by Jim Butcher. Felix Castor is an exorcist, who also consults with the London police on some of their trickiest cases — but he's also got to cope with zombies and demons, one of whom has possessed his best friend Rafi. The bad news? We've been waiting since late 2009 for the promised sixth book, which Carey called "the one that answers the big questions that have been hanging in the air ever since the first book." So this could be sort of a painful addiction, actually.

2) The Miles Vorkosigan books by Lois McMaster Bujold

We've lost count of how many times we've had friends claimed by Vorkosigan addiction. The symptoms are easy to recognize: an obsession with Barrayaran politics, a tendency to quote Miles Vorkosigan's highly quotable lines, and a tendency to bail on social events with a muttered, "Can't come. There are still Vorkosigan books I haven't read yet." Miles Vorkosigan, the hero of Barrayar, is often compared to George R.R. Martin's Tyrion Lannister, and Bujold spends a lot of time exploring the implications of futuristic technology such as uterine replicators and terraforming, while also giving you a cracking good read.

3) Terry Pratchett's Discworld novels

These are actually a number of series contained within a shared universe, the world of Discworld, which is indeed disc-shaped and balanced on the backs of four elephants, which in turn are on a giant turtle. And they're utterly absorbing, thanks to Pratchett's mixture of lovable characters and wry wisdom, mixed with zany humor. Just the four YA-oriented Tiffany Aching books, by themselves, would make for enough of an addictive series for most authors, with their themes of power and responsibility and tiny little angry blue men. But there's also the City Watch books and the Rincewind tales, and so much more. Pratchett's daughter Rhianna has been anointed to take over the series, so here's hoping we continue to be supplied with amazing Discworld books for years to come.

4) Seanan McGuire's October Daye novels

Like the Felix Castor books and many other series, McGuire's urban fantasy series combines some pulpy detective tropes with fantasy elements — but these are even more crammed with fantasy goodness, including fairy kingdoms all over the San Francisco Bay Area and the mysterious King of Cats. The worldbuilding in this series is pretty fantastic, and we've lost count of how many of our friends have raved about the fact that it actually gets better and better after the first couple books. If you've been obsessively watching Lost Girl and need something to tide you over until the next season, this series about a half-fae detective in the dark city might just do the trick.

5) Iain M. Banks' Culture novels

Like Discworld, this is more of a shared universe than a series with the same characters in each book — but Banks creates a universe that's impossible to resist. There's the fascination of imagining just what it would be like to be a Special Circumstances operative, working with the super-intelligent and notoriously perverse artificial intelligences (or Minds) that run the Culture — but there's also all of the tricky questions that tend to arise when a massive, super-advanced post-scarcity civilization bumps up against more primitive cultures and worlds. Banks' plots are always fascinating and thrilling, but there's usually a fascinating set of philosophical questions buried in there as well.

6) The Watch Series by Sergei Lukyanenko

You might know this series thanks to the two Russian vampire movies made by Wanted director Timur Bekmambetov — but the books are even better, says Nightshifted author Cassie Alexander. "Those were the bomb," she adds. "The Nightwatch Series is awesome — and yeah, it was like the movie, only the books made sense." Not only that, but the five-book series ends incredibly well, "but if he came up with another one, I would pay blood to read it."

7) The Company books by Kage Baker

Baker's novels about time-traveling cyborgs who plunder history for their corporate masters in the 24th century tend to suck you in — and maybe it's partly because they contain the best of several genres, including time travel, steampunk, alternate history, and space adventure. As we wrote a few years ago, these books combine, "time-traveling adventure, humor, conspiracy, romance and chocolate."

8) The Patternmaster series by Octavia Butler

Butler wrote five books in the Patternist universe, and they range from the past to the far future. Wild Seed runs from the past up to the present day, and Patternmaster takes place thousands of years in the future, while the other three books are in the present or near future. And as with all of Butler's works, these books suck you in with their explorations of power, hierarchy and exploitation. With near-immortal telepaths who have the power to shape human history, Butler is able to ask the really huge questions about humanity, without necessarily force-feeding you an answer.

9) The Book of the New Sun by Gene Wolfe

And then there's Wolfe's massively award-winning series, the first four volumes of which follow Severian, an apprentice torturer in a far future where the Earth is dying. You can spend hours and hours delving into theories and ideas about the allegorical meaning and secrets contained within these books — or you can just get completely absorbed by Severian's journey, and the fascinating world he explores. This is another series that Alexander recommends as basically being compulsive reading, that you wish there would be more and more of.

10) The Temeraire books by Naomi Novik

And finally, there's one last hit of fantasy crack, with Novik's alternate history featuring dragons in the Napoleonic era. At first, these books hook you with the thrill of learning about the dragons, but over time, they keep you hooked with learning about the way the world has been completely changed as a result of having another intelligent species sharing it with us. This series explores a very different version of our world, piece by piece, and it's an ongoing thought experiment that will keep you fascinated.